Save settings instead of crashing. Sorry about that!

AutoTest: included

It is now possible to choose between case-sensitive or case-insensitive
completion. Also, you can now disable the automatic insertion of braces.

To match the class name, CppToolsPlugin.

without that, the auto-included highly complex files from mkspecs/ make
it spew out oodles of warnings.
by default, the user-provided files are still scanned in "cumulative"
mode (ignoring conditionals), so we collect as many files as possible.
(ported from qt)

code mostly c&p-d from qmake (sync from qt).

use qset instead of qlist

(merge aa87b75910a99a26e7ec581aa38f8982fe231ad0 from qt)

just put the actions into an action group

Done based on new IQuickOpenFilter property, isHidden.

This change removes a number of wrong usages of the CppModelManager::documents()/document().